Space-based gravitational-wave detector may detect strange exoplanets

Enlarge / A depiction of one of the trio of satellites that will form the Laser Interferometer Space Antenna. (credit: NASA)

The first detection of gravitational waves came via an instrument that has to strain to overcome the constant background of vibrations and jolts that occur on Earth. Its success has helped push for the pursuit of a project that would rise above all that noise. LISA—the Laser Interferometer Space Antenna—would detect gravitational waves using the same technique as LIGO but place its hardware in space, free of any ground-based vibrations. Preliminary tests of prototype hardware has found that the idea should work.

LISA isn’t expected to be put in place until the 2030s, but that hasn’t stopped astronomers and physicists from contemplating the things that it might possibly detect. Two of these astronomers, Nicola Tamanini and Camilla Danielski, are now suggesting that LISA could be used to identify a very strange class of planets: heavy planets orbiting binary pairs of white dwarf stars. But because of its exquisite sensitivity, LISA could potentially spot them orbiting outside our own galaxy.

How would this work?

Gravitational waves are produced when any two objects with mass interact, but they’re too tiny to be detected unless the objects in question are both massive and near to each other. The LIGO detector is sensitive enough to pick up things like neutron stars and black holes, all of which are both incredibly dense and have masses on the order of the Sun’s and larger. But—due to its enhanced sensitivity and the frequencies of gravitational waves that it will be sensitive to—LISA will be able to pick up objects that are dense but not as massive.